CRM not pulling

njhardy · Post by **njhardy** » 08 Sep 2011, 01:34

Hi all, I have a problem with my Mk3 CRM250 'bogging down' and refusing to pull properly over about 5000 rpm. It has great power low down and revs freely when not in gear. The plug is showing an ok mixture, the power valve seems to be working and the carb settings seem to be ok. The ecu seems to be letting the electrics work ok also. Any suggestions?

Post by **knackeredMk1** » 08 Sep 2011, 09:07

Double check that the powervalve is working correctly as these are classic syptoms of the PV not working. See topic in 'Honda CRM250 FAQs'...............

Second cause may be blocked jet in the carb. Take this off and give it a good clean.

Also may be caused by weak spark. Due to duff spark plug or dodgey electrics.

Post by **Eddie Evans** » 08 Sep 2011, 09:46

Snapped powervalve cable the most likely cause.

njhardy · Post by **njhardy** » 08 Sep 2011, 11:29

thanks guys- will check these items again.

Post by **fallenmikethebike** » 08 Sep 2011, 19:49

Too much fuel at half-ish revs?, It could also be worth having a gander at the needle valve.
They do wear,it only takes a few minutes to check, and possibly raise the clip one notch, and give her a gentle run out, and check for any hesitation.
Is the air filter over oiled?
What's the main jet size?
What pipe is the bike on?
Mike

Post by **back off road** » 08 Sep 2011, 22:24

sounds like a carb problem or a coil breaking down at high revs

njhardy · Post by **njhardy** » 09 Sep 2011, 02:54

Got a Procircuit platinum pipe with an RSV tailpipe- I am going to check its not oiled up this weekend by flushing it out.
Had the carb serviced last weekend, but will check for a worn needle valve. I fiddled with the idle and it just died- so could be more crap in the float chamber/main jet. The air filter had no/little oil on it, so I assumed it would help it run leaner, as the plug was a bit dark.... Hoping its not an electrical problem, as it revs ok when standing and pulls well low down- this is why I'm supecting a stuck powervalve with some crap in the carb.
I have Boysen two stage reed valves in it, and wondering if the reeds maybe cracked or stuck??

Nick

njhardy · Post by **njhardy** » 11 Sep 2011, 04:03

Well, after dismantling the carb and cleaning the jets and resetting the float tang height, then adjusting the power valve- which was way out (by the way, I seem to have 2 lines indicating the correct setting for the powervalve!?!- does this indicate the range it can be set between?) but she fired up eventually with a new plug and I leaned off the mixture and needle height. So she seemed to work fine and was pulling like a steam train and showing all of her 40 hp!!- I was well chuffed with my efforts!!!

Started her up this morning with one kick- great, I thought, we are ready for a bit of 'off roading'! Went for a little blast, but after 2/3 Km she was revving her head off on tickover and then promptly cut out all together. Got her started eventually with a lot of fiddling, but not sure why- she did exactly the same thing after 1km. Did this all the way home- 3 more times. It seems to be either a carb problem, or a heat related problem when she gets hot. I think I read another post about something similar, but nobody really had an answer......any ideas??

Nick

Post by **fallenmikethebike** » 11 Sep 2011, 08:17

The heat is exposing an air leak, usually the cause is the rubber inlet boot, between the carb and the manifold.
Others?
Mike

Post by **back off road** » 11 Sep 2011, 10:17

sounds like running lean with the revving itself up ,plug chop time get the mixture right asap or it WILL be expensive

Post by **fallenmikethebike** » 11 Sep 2011, 10:33

Bit of a long shot here, the spring clip that holds the retaining plate for the needle hasn't been left out, incorrectly installed by any chance?
As B.O.R. has said, it's running seriously lean, is the filter clean and oiled, as already mentioned, what's the plugs story?
Is the carb back in the inlet boot snugly, and tightened down.
Check the cable run at the top of the carb for kinking, and seizure of the inner cable.
Can you hear the throttle body dropping back against the tick over screw when the twist grips released.
Mike

njhardy · Post by **njhardy** » 12 Sep 2011, 03:05

Will recheck all these things.

Did a plug chop and the brand new plug looks ok- light brown with a bit of grey, so will richen the mixture a bit. I did take the needle down 2 clips as it was running filthy rich previously, so maybe that was too much? I will check for snagging of the spring and cable too and make sure the boot is sealed. Could it be the reed valves sticking?

Having read another post about an electrical fault in the coil or key switch (which sounded similar), it has got my head spinning- so many places to check..... Bits for the CRM are impossible to get here in 'Nam, so Iwant to avoid going to a local mechanic, because they just 'cut and chop' from other bikes and 'make things fit'! -This is a place I don't want to be at!!

Nick

CRM not pulling

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